The 23-storey tall Falcon Heavy roared off its launch pad at 3:45 p.m. ET at the Kennedy Space Center, from the same site used by NASA’s towering Saturn 5 rockets to carry Apollo missions to the moon more than 40 years ago.

Though the maiden launch is unmanned, there is a special payload: a Tesla roadster destined to orbit the sun between Mars and Earth.

What is the Falcon Heavy?

SpaceX’s workhorse rocket is the Falcon 9, named for its number of engines. It’s used to launch satellites and for supply missions to the International Space Station.

What makes the Falcon 9 special is its reusability: Once launched, the rocket’s first stage returns to Earth, landing at Cape Canaveral.

The Heavy is made up of three Falcon 9s — two of them launching today have been used before — for a total of 27 engines.

It should be capable of lifting some 63,800 kilograms into low-Earth orbit (LEO). The Delta IV Heavy, currently the most powerful rocket in production, can carry roughly 22,560 kilograms.

What’s the big deal?

The launch is potentially historic: not only would it be the most powerful rocket in production, but it would also be the first such rocket built by a private company. As well, it would be the first time that three boosters would land back on Earth simultaneously.

SpaceX founder and CEO Elon Musk has long said his goal is to make access to space affordable and his reusable rockets are what’s cutting the costs. The Falcon Heavy has a price tag of $90 million per launch compared to more than $1 billion for the second most powerful rocket, the United Launch Alliance’s Delta IV Heavy.

“This is a big first for just getting things into low-Earth orbit, but it’s also a big deal for commercial space because a company is about to put potentially 140,000 pounds into low-Earth orbit, years ahead of NASA’s expensive Space Launch System,” said space historian Randy Attwood, referring to NASA’s next-generation rocket, which is scheduled to launch in 2020.

“They’re doing it earlier, they’re doing it cheaper and the capability of the first stage is incredible.”

“It represents big changes in space in the future in that it’s going to get cheaper to space which means we’ll be doing more of space, which I think is good for humanity,” Canadian astronaut Jeremy Hansen told CBC News.

“This rocket represents progress for SpaceX, and they’re already making a great contribution to space exploration and utilization of space,” he said.

What’s inside?

Musk, who is also CEO of the electric car company Tesla, is having fun with this launch.

For Heavy’s maiden voyage, Musk has used a cherry red Tesla Roadster as the payload — complete with a dummy named Starman.

As Musk posted on Instagram on Monday afternoon, “If it doesn’t explode into tiny pieces, it will carry Starman in Roadster over 400 million km from Earth at 11 km/sec on a billion year journey through deep space.”

There will also be three cameras aboard the car as it heads to Mars. Once there, it will continue to orbit the sun between Earth and Mars for millions or billions of years.

And of course, Starman is wearing the newly designed spacesuit astronauts will be donning aboard the crew capsules currently in production by SpaceX.

Normally, Musk said, he feels nervous ahead of a launch. But not this time.